WIP: Fix collective.recipe.shelloutput return code
collective.recipe.shelloutput is a handy recipe to include the output of a shell command in buildout, unfortunately it does not check return code of that shell command.
To workaround this, we are using it with plone.recipe.command, which checks the return code, but I missed that it only checks the return code when stop-on-error was true.
This change is about setting stop-on-error to true so that this trick works as expected.